Bedded underground salt deposit solution mining system

ABSTRACT

An improved system for coalescing the nether ends of a group of spaced-apart bore holes intersecting a bedded rock salt deposit, and for instituting and controlling progress of a solution-mining operation thereon. The invention is particularly useful in coalescing two or more bore holes extending into a bedded rock salt deposit whenever conventional hydraulic fracturing methods prove inadequate, such as by reason of the existence of faults or other anomalies existent intermediately of the bore holes. The system employs a flexible solvent delivery tube slip-fitted downwardly through one of the bore holes into the salt deposit; it being arranged that the delivery or nozzle end of the tube floats and travels horizontally along a gravitymonitored interface between the input solvent and resultant brine mixture and a thereabove maintained solvation insulating pad of oil or some other suitable hydrocarbon gas or air or the like, which at this stage operates to prevent undesirable upward progression of the solution mining process. The solvent delivering nozzle is at all times directionally controlled in an improved manner throughout the coalescing/mining operations in conjunction with an improved advancing/retreating mining method.

[ Mar. 25, 1975 -mining operation [57] ABSTRACT An improved system forcoalescing the nether ends of a group of spaced-apart bore holesintersecting a beded rock salt deposit, and for instituting andcontrolling progress of a solution thereon. The invention isparticularly useful in coalescing two or more bore holes extending intoa bedded rock salt deposit whenever conventional hydraulic fracturingmethods prove inadequate, such as by reason of the existence of faultsor other anomalies existent intermediately of the bore holes. The systememploys a flexible solvent delivery tube slip-fitted downwardly throughone of the bore holes into the salt deposit; it being arranged that thedelivery or nozzle end of the tube floats and travels horizontally alonga gravitymonitored interface between the input solvent and resultantbrine mixture and a thereabove maintained solvation insulating pad ofoil or some other suitable hydrocarbon gas or air or the like, which atthis stage operates to prevent undesirable upward progression of thesolution mining process. The solvent delivering nozzle is at all timesdirectionally controlled in an improved manner throughout thecoalescing/- mining operations in conjunction with an improvedadvancing/retreating mining method.

19 Claims, 6 Drawing Figures 299/4 299/4 299/4 Dahms et E2lb 43/28299/4, 5, l7; l66/27l; 175/61, 231

SOLUTION MINING SYSTEM Inventor: Charles H. Jacoby, Dalton, Pa.

Assignee: Akzona Incorporated, Asheville,

Filed: Feb. 26, 1974 Appl. No.: 445,975

Related US. Application Data Continuation of Ser. No. 324,005, Jan.

abandoned.

U.S. 299/4, 166/271, l75/6l, 175/231, 175/422, 299/17 Field of SearchReferences Cited UNITED STATES PATENTS 2,822,158 2/1958 9/1958Hanson....,....... 10/1967 Dahms et 3,402,965 9/1968 Unlted StatesPatent Jacoby BEDDED UNDERGROUND SALT DEPOSIT Primary Examiner-Ernest R.Purser Attorney, Agent, or Firm-Bean & Bean INSOLU BLE ROCK PATENTED9,873,156

HYDRAULIC FRACTURED AREA I5.

1 BEDDED UNDERGROUND SALT DEPOSIT SOLUTION MINING SYSTEM This is acontinuation of application Ser. No. 324,005, filed Jan. 15, 1973, andnow abandoned.

BACKGROUND AND BRIEF DESCRIPTION OF THE INVENTION In solution miningoperations, one or more bore holes are typically provided to penetratethe overlying geological formations so as to reach the subterraneansought-for" or product mineral, and means are thereupon employedto'establish therein an open cavity or passageway whereby the mineralmay be extracted by circulation therethrough of a suitable solvent suchas water, acid, steam, or some other solvent liquid or gas such as isunsaturated with respect to the sought-for mineral.

. It is known that the efficiency of a solution mining cavity system isimproved as the dimensions of the fluid travel path within the cavityincrease. Such flow patterns are typically enhanced when initiatng asolution mining operation by establishing as soon as possible a cavityof substantial horizontal (as well as vertical) extent between the pointof solvent injection and the point of effluent withdrawal; because suchcavities inherently tend to automatically increase vertically. In acavity which is in communication with a single duplexcased bore hole theoperation is of course at first limited to the vertical distance betweenthe injection and withdrawal ports of the bore hole casing system; andtherefore it is preferred to employ a plurality of bore holes andconventional hydraulic fracturing operations with a view to establishingsolution conveying cavities therebetween. For example, reference is madeto my prior US. Pat. Nos. 3,064,957 and US. Pat. No. Re. 25,682.

However, in many cases it is found to be impossible to satisfactorilycoalesce the bottoms of two or more bore holes by such hydraulicfracturing methods be cause ofthe intervention of geological anomaliestherebetween. The present invention provides an improved method forrapidly coalescing the lower ends of two or more such bore holes whendriven into a rock salt bed and when encountering such an anomalies,therebyestablishing solvent passageways therethrough which are orientedin generally horizontal direction between the bottoms of such boreholes, and for subsequently conducting an improved technique forsolution mining the salt bed.

THE DRAWING F IG. 1 is afragmentary vertical geological sectionillustrating compositely successive stages of a coalescing operation inaccordance with the present invention; designed specifically to overcomeencounter with a fault system such as typically forestalls successfulcompletion of a conventional hydraulic fracturing fluid passagewayforming operation;

FIG. 2 is a horizontal sectional view taken as indicated by line 2--2 ofFIG. 1;

FIG. 3 is a view corresponding to FIG. 1 but illustrating completion ofa solution-flow passageway between the two bore holes such as may beestablished by my new process;

FIG. 4 is a view corresponding to FIGS. 1 and 3; illustratin gprogressive stages of the subsequently employed solution miningtechnique in accordance with the invention;

FIG. 5 is a fragmentary illustration of one form of a directionallycontrollable solvent delivery nozzle such 5 as may be used inconjunction with the invention; and

FIG. 6 illustrates another form of self-motivating sol vent deliveringnozzle such as may be used in accordance with the invention.

DETAILED DESCRIPTION OF THE INVENTION By way of example and referringnow to FIGS. 1 and 2 of the drawing herewith, a pair of bore holes 10,12 may be driven to intersect a soluble deposit 14 of bedded salt or thelike, and cased preferably to a level close to the bottoms thereof. Thedrawing illustrates a geologic condition typically encountered when boreholes are driven into a bedded salt deposit with a view tointerconnecting their bottom ends as by means of a hydraulic fracturingoperation (such as illustrated and described in detail in my prior US.Pat. Nos. 3,064,957 and Re. 25,682).

In the illustration herewith the hydraulically fractured zone 15 whichradiates from the bottom of bore hole 12 has encountered a geologicalfault 16; whereby the attempt to interconnect the bore holes 10-12 bymeans of a propped fracture has failed. Such geological anomalies oftenoccur for example throughout the greatAppalachian Salt Basin beds whichunderlie many of the Eastern States; and may appear in the form of openor closed faults; sharp foldings; crevices filled with insoluble debris;and/or the like. The present invention provides an improved method forcompleting a solvent fluid flow passageway between bore holes such asare described hereinabove, and also provides an improved solution miningsystem as illustrated at FIGS. 3 and 4 herewith.

In accordance with this invention, assuming that an attempt tohydraulically fracture the lower portion of the salt bed 14 to provide apropped" passageway from bore hole 12 to bore hole 10 has met with afault zone such as is shown at 16, the bore hole 10 is thereupon flttedwith a casing 20; the lower end of the casing 20 being provided with asmoothly curved laterally directed outlet cuff as is illustrated at 22.A solvent delivery tube of flexible nature as illustrated at 25 is thenslide-fitted downwardly through the casing 20 so as to project at thelower end thereof through the exit cuff 22 in the desired horizontaldirection. A solvent fluid is then pumped through the tube 25 to jettherefrom in a horizontal direction against the opposing salt face,whereby the jetted fluid dissolves the salt away while returning it tothe earth surface recovery facility in the form of brine, through theannulus surrounding the tube 25.

In order to direct the solvent jet action so as to progress horizontallyfrom the bore hole 10 toward the bore hole 12 until such time as thesolvated cavity eroded through the fault zone 16 and connects with thepreviously hydraulically fractured passageway 15, one or more floatssuch as are shown at 26-28 are fixed upon the nozzle end 30 of the tube25 in spaced-apart relation thereon in such manner as to cause thenozzle end of the tube to float horizontally at or near the top of thesolvent-brine mixture within the cavity. Thus, the jet nozzle isprevented from dipping or rearing upwardly so as to direct the solvatingprocess on a downwardly or upwardly on an inclined path, such as wouldmiss connection with the fractured zone 15.

As a further assist at this stage in preventing any undesirable upwarderosion of the salt body above the level of the intended channel to beeroded toward the fault zone, a solvation insulatng pad" or blanket ofoil or air or gas or the like may be introduced and maintained to floaton top of the desired level of the solvent/brine solution throughout theoperation. For this purpose the oil (or the like) may be simply added inproper proportion to the solvating liquid as the latter is furnishedthrough the bore hole 10. The floats 26-28 are fabricated so that thetube-float combination is of slightly greater specific gravity than thematerial comprising the pad, while being of lower specific gravity thanthat of the solvent/brine mixture at the bottom of the cavity. Forexample, the floats may be made of any suitable solids such as wood,foamed plastic, glass or the like; and/or may be of inflatable form,such as may be preferred.

When operating within a geologic deposit of the type where thesought-for soluble mineral rests upon an underlying insoluble rock sillalong a substantially flat and clean parting plane, and jet nozzle 30may be provided with a self-motivating traction device such as isillustrated at FIG. 6 of the drawing herewith. As shown herein at 32 thecasing of the jet nozzle is slotted to accommodate pinwheels 34 whichare pivotally mounted as by means of fins 36 on the nozzle casing so asto extend into the slots 32. Thus, as the solvent fluid jets through thenozzle device, the pinwheels are driven hydrodynamically wherebywhenever their outside portions engage the cavity floor surface theytend to drag the nozzle forwardly in the direction of the jet discharge.It is to be understood however that any other suitable mechanism forforwardly propelling the nozzle end of the tube 25 may be employed, suchas for example a remotely controlled motor unit.

To provide suitable directional control of the nozzle progress withinthe horizontal plane parameters established by the aforesaid devices; itis contemplated that a variety of means may be employed for suchpurpose. For example, the progress of the nozzle 30 may be guided fromabove ground by simply twisting the upper end of the tube 25 where itexists above ground from the bore hole casing. Or, the nozzle may beconstructed to include an automatically or remotely controlled guidancedevice such as my include alternatively operable jet-exit side ports 38as shown in FIG. or an electronically operated guidance mechanism suchas may cause the nozzle to seek or home-in" on a target device placed inthe bottom end of the'bore hole 12. In any case the mechanism would beunder remote control by the process operator and/or monitoredautomatically; as for example by a bore hole surveying type device orthe like, such as is indicated at 40 (FIG. 5).

FIG. 4 illustrates how the soluble mineral deposit is preferably minedsubsequent to coalescing the bottom ends ofthe bore holes -l2 asexplained hereinabove. Operation of the float 28 atthe nozzle end of thesolvent delivery tube is altered so as to overcome the prior tendency tomaintain the nozzle in horizontally directed attitude and to permit itto point upwardly; thereby causing the solvent jet discharge to sweepthe salt bed 14 in an upwardly directed path. This may be readilymanaged either by inflating the float 28 to a larger volume or bysubstituting a more buoyant float for the one originally mounted on thenozzle end of the tube; the tube 25 being temporarily withdrawn back upthe bore hole 10 to enable such an exchange to be made. Then, asthe'upturned nozzle operates to direct the solvent fluid to mine thesalt bed up to the desired ceiling level the delivery tube may be slowlyretracted (by pulling upon its outer end) so as to cause the upturnednozzle to drive the solvent fluid against the overlying salt bed inaccordance with a progressively retreating solution mining operationsuch as is diagrammatically illustrated at FIG. 4.

I claim:

1. The method for solution-coalescing the nether ends of two or morebore holes intersecting a bedded rock salt deposit which includes ageologic anomaly preventive of effectively coalescing said bore holes bymeans of a hydraulic fracturing technique, and for conducting a solutionmining operation throughout said deposit, said method comprising:

driving two or more bore holes in spaced apart relation into the lowerlevel of said deposit at opposite sides of said anomaly,

hydraulically fracturing said deposit from one of said bore holes as faras feasible towards one other of said bore holes, thereby providing afirst horizontally extending passageway for fluid flow,

then solution-mining a second horizontally extending passageway from thenether end of the other of said bore holes through said salt bed andthrough said anomaly into communication with said first passageway,thereby providing a solution mining cavity,

and then solution mining said deposit intermediately of said bore holesby passing a solvent fluid through said cavity from one of said boreholes and withdrawing brine out of the other of said bore holes wherebysaid cavity enlarges and said deposit is mined.

2. The method for coalescing the nether ends of two or more bore holesintersecting a bedded rock salt deposit and for conducting a solutionmining operation throughout said deposit as set forth in claim 1,wherein said solution mining operation is conducted by means of solventliquid delivered through a flexible hose slidefitted into and advancedthrough one of said bore holes and having guide means thereon to causethe nozzle end thereof to point substantially horizontally towards thenether end of the other of said bore holes.

3. The method of coalescing the nether ends of two or more bore holesintersecting a bedded rock salt deposit and for conducting a solutionmining operation throughout said deposit as set forth in claim 1,wherein said solution mining operation is conducted under asolvent-insulating pad of fluid at the ceiling of the solution miningcavity.

4. The method of coalescing the nether ends of two or more bore holesintersecting a bedded rock salt deposit and for conducting a solutionmining operation throughout said deposit as set forth in claim 2,wherein said nozzle end of said hose carries a motivating device poweredunder remote control and operating to advance the nozzle end of saidhose toward said other bore hole.

5. The method of coalescing the nether ends of two or more bore holesintersecting a bedded rock salt deposit and for conducting a solutionmining operation throughout said deposit as set forth in claim 2,wherein the solution mining operation upon said deposit is initiallyconducted proximate to said other bore hole and is then caused toretreat progressively throughout the deposit intermediately of said boreholes by progressive retraction of said hose.

6. The method of coalescing the nether ends of two or more bore holesintersecting a bedded rock salt deposit and for conducting a solutionmining operation throughout said deposit as set forth in claim 3,wherein said guide means comprises a float device carried adjacent thenozzle end of said hose, said float device being operable to cause thenozzle end of said hose to float at substantially the elevation of theinterface between the brine and the solution insulating pad fluidoccupying the solution cavity.

7. The method of coalescing the nether ends of two or more bore holesintersecting a bedded rock salt deposit and for conducting a solutionmining operation throughout said deposit as set forth in claim 4,wherein said motive device comprises a traction wheel system powered byflow of fluid through said nozzle.

8. The method of coalescing the nether ends of two or more bore holesintersecting a bedded rock salt deposit and for conducting a solutionmining operation throughout said deposit as set forth in claim 2,wherein said guide means comprises multi-radially directed reaction jetports exiting through the wall of said nozzle, said ports beingselectively controllable from remotely of the operation.

9. The method of coalescing the nether ends of two or more bore holesintersecting a bedded rock salt deposit and for conducting a solutionmining operation throughout said deposit as set forth in claim 3,wherein said solvent insulating pad comprises a fluid of lower specificgravity than brine and which is introduced into the solution miningcavity as an additive to the solvent fluid.

10. The method of coalescing the nether ends of two or more bore holesintersecting a bedded rock salt deposit and for conducting a solutionmining operation throughout said deposit as set forth in claim 2,wherein said guide means comprises a plurality of float devices spacedapart longitudinally on said hose so as to stabilize a substantiallength thereof in horizontal attitude.

11. The method of solution-coalescing the nether ends of two or morebore holes intersecting a bedded rock salt deposit which includes ageologic anomaly preventive of effectively coalescing said bore holes bymeans of a hydraulic fracturing technique, said method comprising:

driving two or more bore holes in spaced apart relation into saiddeposit at opposite sides of said anomaly;

hydraulic fracturing said deposit from one of said bore holes as far asfeasible towards another of said bore holes, thereby providing a firstextending passageway for fluid flow; and

solution mining a second extending passageway from said another of saidbore holes through said salt bed and through said anomaly intocommunication with said first passageway.

12. The method for coalescing the nether ends of two or more bore holesof claim 11 wherein said solution mining is conducted by means ofsolvent liquid delivered through a flexible hose advanced through saidanother bore hole, said flexible hose being fitted with a nozzle havingmeans for guiding the nozzle end substantially towards said firstpassageway.

13. The method of coalescing the nether ends of two or more bore holesas set forth in claim 12 wherein said guide means include reaction jetports exiting throught the wall of said nozzle, said jet ports beingselectively operable.

14. The method of coalescing the nether ends of two or more bore holesas set forth in claim 12 including inserting a target device in saidfirst passageway and wherein said guide means include an electronicallyoperated guidance mechanism to home-in on said target device.

15. The method of coalescing the nether ends of two or more bore holesas set forth in claim 12, wherein said guide means include a directionaland inclination surveying device.

16. The method of coalescing the nether ends of two or more bore holesas set forth in claim 11, including forming a solvation insulating padat the ceiling of said second passageway.

17. The method of coalescing the nether ends of two or more bore holesas set forth in claim 16 wherein said solvation insulating pad comprisesa fluid of lower specific gravity than brine, including the step ofintroducing said pad fluid into said second passageway as an additive tothe solvent fluid for said solution mining.

18. The method of coalescing the nether ends of two or more bore holesas set forth in claim 16 including floating the nozzle substantially atthe interface between said solvation insulating pad and the brine/solvent mixture formed in the lower part of said second passageway.

19. The method of solution mining a bedded rock salt deposit between twoor more bore holes comprising the steps of coalescing the nether ends ofsaid bore holes by the method of claim 11 and thereafter solution miningsaid deposit beginning in the region of said first passageway andretreating progressively toward said second passageway and said anotherbore hole.

1. The method for solution-coalescing the nether ends of two or more bore holes intersecting a bedded rock salt deposit which includes a geologic anomaly preventive of effectively coalescing said bore holes by means of a hydraulic fracturing technique, and for conducting a solution mining operation throughout said deposit, said method comprising: driving two or more bore holes in spaced apart relation into the lower level of said deposit at opposite sides of said anomaly, hydraulically fracturing said deposit from one of said bore holes as far as feasible towards one other of said bore holes, thereby providing a first horizontally extending passageway for fluid flow, then solution-mining a second horizontally extending passageway from the nether end of the other of said bore holes through said salt bed and through said anomaly into communication with said first passageway, thereby providing a solution mining cavity, and then solution mining said deposit intermediately of said bore holes by passing a solvent fluid through said cavity from one of said bore holes and withdrawing brine out of the other of said bore holes whereby said cavity enlarges and said deposit is mined.
 2. The method for coalescing the nether ends of two or more bore holes intersecting a bedded rock salt deposit and for conducting a solution mining operation throughout said deposit as set forth in claim 1, wherein said solution mining operation is conducted by means of solvent liquid delivered through a flexible hose slide-fitted into and advanced through one of said bore holes and having guide means thereon to cause the nozzle end thereof to point substantially horizontally towards the nether end of the other of said bore holes.
 3. The method of coalescing the nether ends of two or more bore holes intersecting a bedded rock salt deposit and for conducting a solution mining operation throughout said deposit as set forth in claim 1, wherein said solution mining operation is conducted under a solvent-insulating pad of fluid at the ceiling of the solution mining cavity.
 4. The method of coalescing the nether ends of two or more bore holes intersecting a bedded rock salt deposit and for conducting a solution mining operation throughout said deposit as set forth in claim 2, wherein said nozzle end of said hose carries a motivating device powered under remote control and operating to advance the nozzle end of said hose toward said other bore hole.
 5. The method of coalescing the nether ends of two or more bore holes intersecting a bedded rock salt deposit and for conducting a solution mining operation throughout said deposit as set forth in claim 2, wherein the solution mining operation upon said deposit is initially conducted proximate to said other bore hole and is then caused to retreat progressively throughout the deposit intermediately of said bore holes by progressive retraction of said hose.
 6. The method of coalescing the nether ends of two or more bore holes intersecting a bedded rock salt deposit and for conducting a solution mining operation throughout said deposit as set forth in claim 3, wherein said guide means comprises a float device carried adjacent the nozzle end of said hose, said float device being operable to cause the nozzle end of said hose to float at substantially the elevation of the interface between the brine and the solution insulating pad fluid occupying the solution cavity.
 7. The method of coalescing the nether ends of two or more bore holes intersecting a bedded rock salt Deposit and for conducting a solution mining operation throughout said deposit as set forth in claim 4, wherein said motive device comprises a traction wheel system powered by flow of fluid through said nozzle.
 8. The method of coalescing the nether ends of two or more bore holes intersecting a bedded rock salt deposit and for conducting a solution mining operation throughout said deposit as set forth in claim 2, wherein said guide means comprises multi-radially directed reaction jet ports exiting through the wall of said nozzle, said ports being selectively controllable from remotely of the operation.
 9. The method of coalescing the nether ends of two or more bore holes intersecting a bedded rock salt deposit and for conducting a solution mining operation throughout said deposit as set forth in claim 3, wherein said solvent insulating pad comprises a fluid of lower specific gravity than brine and which is introduced into the solution mining cavity as an additive to the solvent fluid.
 10. The method of coalescing the nether ends of two or more bore holes intersecting a bedded rock salt deposit and for conducting a solution mining operation throughout said deposit as set forth in claim 2, wherein said guide means comprises a plurality of float devices spaced apart longitudinally on said hose so as to stabilize a substantial length thereof in horizontal attitude.
 11. The method of solution-coalescing the nether ends of two or more bore holes intersecting a bedded rock salt deposit which includes a geologic anomaly preventive of effectively coalescing said bore holes by means of a hydraulic fracturing technique, said method comprising: driving two or more bore holes in spaced apart relation into said deposit at opposite sides of said anomaly; hydraulic fracturing said deposit from one of said bore holes as far as feasible towards another of said bore holes, thereby providing a first extending passageway for fluid flow; and solution mining a second extending passageway from said another of said bore holes through said salt bed and through said anomaly into communication with said first passageway.
 12. The method for coalescing the nether ends of two or more bore holes of claim 11 wherein said solution mining is conducted by means of solvent liquid delivered through a flexible hose advanced through said another bore hole, said flexible hose being fitted with a nozzle having means for guiding the nozzle end substantially towards said first passageway.
 13. The method of coalescing the nether ends of two or more bore holes as set forth in claim 12 wherein said guide means include reaction jet ports exiting throught the wall of said nozzle, said jet ports being selectively operable.
 14. The method of coalescing the nether ends of two or more bore holes as set forth in claim 12 including inserting a target device in said first passageway and wherein said guide means include an electronically operated guidance mechanism to home-in on said target device.
 15. The method of coalescing the nether ends of two or more bore holes as set forth in claim 12, wherein said guide means include a directional and inclination surveying device.
 16. The method of coalescing the nether ends of two or more bore holes as set forth in claim 11, including forming a solvation insulating pad at the ceiling of said second passageway.
 17. The method of coalescing the nether ends of two or more bore holes as set forth in claim 16 wherein said solvation insulating pad comprises a fluid of lower specific gravity than brine, including the step of introducing said pad fluid into said second passageway as an additive to the solvent fluid for said solution mining.
 18. The method of coalescing the nether ends of two or more bore holes as set forth in claim 16 including floating the nozzle substantially at the interface between said solvation insulating pad and the brine/solvent mixture formed in the lower part of said second passageway.
 19. The method of solution mining a bedded rock salt deposit between two or more bore holes comprising the steps of coalescing the nether ends of said bore holes by the method of claim 11 and thereafter solution mining said deposit beginning in the region of said first passageway and retreating progressively toward said second passageway and said another bore hole. 